项目中引用web3sdk，出现no content to map

排查后，发现是netty的版本问题，在web3sdk中引用的netty版本是4.1.15.final
问题在于：

1. 因为web3sdk没有在maven仓库中有相关的版本，项目不能直接添加maven引用，只能本地引用jar lib
2. web3sdk的readme中没有强调第三方jar包的依赖关系，建议写上

Open the web3sdk README and inspect its dependency and setup instructions, especially the Netty 4.1.15.Final and local JAR references mentioned in the issue. Done means the README clearly lists the required third-party JAR dependencies and explains the Maven/local-library limitation related to the reported no-content-to-map problem.

Written by the indexing model from the issue text.